Automatic tensioner



June 9, 1964 J. J. MURRAY AUTOMATIC TENSIONER Filed Dec. 26, 1962INVENTOR. JAMES J MU RRAY ATTORNEY United States Patent lice 3,136,170AUTOMATIC TENSIONER James J. Murray, 14011 Oakland Ave, Detroit 3, Mich.Filed Dec. 26, 1962, Ser. No. 247,091 4 Claims. (Cl. 74-242.11)

This invention relates to power transmission and particularly to thetransmission of power by chain or belt driven mechanisms.

An object of the invention is to provide a device which willautomatically maintain tension on a chain or belt drive.

Another object of the invention is to provide a device of the characterindicated which is particularly suitable for use on power drives whichhave both forward and reverse action.

A further object of the invention is to provide a device of thecharacter indicated, which is constructed and arranged so that it willautomatically maintain tension on a fixed-center drive, whether it isoperating in a forward or reverse direction.

Another object of the invention is to provide a chain or belt tensionerwhich consists of a minimum number of parts, is economical tomanufacture, and is easy to install on new or old equipment withoutspecial tools.

Another object of the invention is to provide a device of the characterindicated which is constructed and arranged so that it swings from sideto side to automatically accomplish the slack take up, when the drivechanges from forward to reverse.

Another object of the invention is to provide a device of the characterindicated, which is constructed and arranged so that the necessity ofdown time for making adjustments is entirely obviated.

Another object of the invention is to provide a device of the characterindicated, which is constructed and arranged to automatically take upthe slack and to dampen the vibration in a forward and reverse chaindriven ma chine.

Another object of the invention is to provide a device of the characterindicated, which is constructed with a novel spring biased arm, which ispositioned and arranged so that it swings through an arc sufiicient toautomatically take up the slack on both the forward and reverse sides ofa chain drive, whereby to eliminate any tendency of the slack in thechain to damage the equipment by breaking off sprocket teeth, or jammingthe drive by back lash, or by jumping off the sprockets.

The foregoing and other objects and advantages of the invention willbecome more apparent as the description proceeds, reference being madefrom time to time to the accompanying drawings forming part of thewithin disclosure, in which drawings:

FIG. 1 is a plan view, with parts broken away, of a device embodying theinvention.

FIG. 2 is a side elevational of the device shown in;

- FIG. 1, with parts broken away.

FIG. 3 is a section taken substantially on the line 3-3 of FIG. 2.

FIG. 4 is a diagrammatic view of the device shown in FIG. 1, combinedwith a forward and reverse drive mechanism.

Referring now more particularly to the drawings, it will be understoodthat in the embodiment herein disclosed, the reference character 7indicates a base, or mounting plate, having apertures 8 for receivingbolts (not shown) by which the device may be secured to a machine, whichis motivated, as shown in FIG. 4, by a forward and reverse chain drive.

The device is preferably mounted so that the arm 9 3,136,170 PatentedJune 9, 1964 may swing approximately 60 to either side of the positiOnshown in FIG. 1, ment may be as much as on either side.

The arm 9 is bored to receive the pivot shaft 10 which is press fittedor otherwise secured in a bore formed in the base 7.. A suitable bearingelement 12 is positioned between the arm 9 and the shaft 10, so that thearm may freely pivot on the shaft. An idler which may be a sprocket asshown at 13 or a pulley or the like, which 18 pivoted for rotation on apivot shaft 14, which passes through another bore 15 formed in the arm9. The shaft 14 is secured by a nut 16 and is provided with a bearingmember 17, so that the idler sprocket 13 may rotate freely thereon.

The arm 9 is spring loaded as follows: A stiff coil spring 18 is mountedaround, as shown in FIGS. 2 and 3, the pivot shaft 10 and has endextensions 19 and 20 which respectively engage the opposite sides of apair of pins 21 and 22. The pin 21 is an anchor pin and is secured tothe base 7 and the pin 22 is a spring actuating pin and is secured tothe arm 9 and extends through an opening in the top cover plate 23. Thecover plate 23 is in contact with a dust cover 24, which encircles thespring 18 and the shaft 10. The cover plate 23 has a central opening toreceive the pivot shaft 10 and rotates with the arm 9 by means of thepin 22. The assembly is held together by the nut 25 which engages areduced threaded extension 10A of the shaft 10. Washers 26 and 27complete the assembly.

As shown in FIG. 4, the device is mounted so that the idler sprocket 13contacts the chain 28, which engages the driven sprocket 29 and thedrive sprocket 30, which is rotated in forward and reverse directions bya suitable motor (not shown). The solid lines show the chain and tensionarm when in forward direction and the broken lines, show their positionsand relation when in reverse.

When the arm 9 is moved to the left (FIG. 1) the actuating pin 22 willmove the spring extension 19 to the left while the extension 20 is heldby the anchor pin 21. This places tension on the spring 18 in onedirection. When the arm 9 is moved to the right (FIG. 1) the actuatingpin 22 will move the extension 20 to the right while the extension 19 isbeing held by the anchor pin 21. This places tension on the spring 18 inthe opposite direction. When the arm 9 is in the position shown in FIG.1, the spring 18 is balanced and the arm is at rest. As soon as theidler sprocket 13 at the end of the arm 9 is brought into engagementwith the chain 28 (FIG. 4) and the chain 28 is moved, the arm 9 willswing in the direction of the movement of the chain causing tension tobe built up in the spring as described above. On the reverse of thechain tension will build up on the other side of the spring. The springtension so built up, will automatically take the slack out of the chainin forward or reverse motions.

It is believed that the operation of the device is obvious from theforegoing description.

Having described my invention, what I claim and desire to secure byLetters Patent is:

l. A device of the character described, comprising a base plate, a pivotshaft secured to said base, an arm pivotally supported on said shaft, anidler on the free end of said arm, an anchor pin secured to said baseplate, a second pin secured to said arm, and movable therewith, a coilspring surrounding said shaft and having its respective ends positionedon opposite sides of said anchor pin and said second pin and arranged sothat upon a pivotal movement of said arm and said second pin in eitherdirection on said shaft, tension is built up in said spring.

2. The structure of claim 1 in which said anchor pin on said base andthe said pin on said arm when normally at although in extreme cases themove 3 rest are in alignment with the longitudinal axis of saidpivotable arm.

3. The structure of claim 1 in which there is a rotatable cover platespaced from said base plate and a dust cover surrounding said pivotshaft and said spring, and positioned between said base plate and saidcover plate.

4. The structure of claim 1, in which there is rotatable cover platespaced from said base plate and a dust cover surrounding said pivotshaft and said spring, and positioned between said base plate and saidcover plate, there being a hole in said cover plate in which is receivedthe said pin secured to said arm, and a second hole in said cover platefor receiving said pivot shaft whereby to permit said cover plate torotate with said arm about said pivot shaft.

' References Cited in the file of this patent UNITED STATES PATENTSBernhard Nov. 30, 1954

1. A DEVICE OF THE CHARACTER DESCRIBED, COMPRISING A BASE PLATE, A PIVOTSHAFT SECURED TO SAID BASE, AN ARM PIVOTALLY SUPPORTED ON SAID SHAFT, ANIDLER ON THE FREE END OF SAID ARM, AN ANCHOR PIN SECURED TO SAID BASEPLATE, A SECOND PIN SECURED TO SAID ARM, AND MOVABLE THEREWITH, A COILSPRING SURROUNDING SAID SHAFT AND HAVING ITS RESPECTIVE ENDS POSITIONEDON OPPOSITE SIDES OF SAID ANCHOR PIN AND SAID SECOND PIN AND ARRANGED SOTHAT UPON A PIVOTAL MOVEMENT OF SAID ARM AND SAID SECOND PIN IN EITHERDIRECTION ON SAID SHAFT, TENSION IS BUILT UP IN SAID SPRING.